Removal of spent wood chips from extractors used in rosin recovery processes



Patented Apr. 17, 1951 REMovaL OE SBENT W001) o IPs FROM sxraacrocsnspn m-nosm -nroovsnr was L. iee ea e, 111- No Drawing.

p lication SeriallNo. 11,353 1 eb ua y 26, 48,

seems 135 -28,

My invention is concerned with processes relating to the treatment of wood chips in which the rosin,'turpentine, pine oil and other n'aval stores products content thereof are recovered, and is particularly concerned with certain procedures, hereafter described in detail, for facilitatingand rendering more economical such operations.

In the usual processes of treating Wood chips to recover the naval stores content thereof, the chips are placed in so-called extractors, also commonly called retorts or digesters. These extractors, which may vary in size, are usually of cylindrical shape and may, for example, have a height of 16 to 20 feet and a diameter of 7 to 9 feet and may'hold from 8 to 10 tons of wood chips. The chips may be supported on a 'perforated plate mounted in the lower part of the extractor. The extractor is provided with a large door adjacent the lower part thereof. The wood chips, which may be made by cutting and shredding the wood and stumps from the pine off a substantial part of the turpentine and pine oil. The thus treated Wood chips are then sub"- jected to extraction with an organic solvent, for I example, gasoline or other low boiling or volatile petroleum hydrocarbon solvents, at elevated temperature, which dissolves out of the wood chips the rosin, residual turpentine, pine oil and other solvent-soluble ingredients. In usual commercial practice, a series of extractors, say five or six, is subjected, by the multiple extraction process, to the action of the Solvent, the chips in each extractor of the series being washed with several batches of solvent in succession, and each batch of solvent is used to wash the chips in the several extractors in the series. After the final washing of the chips in an extractonthat extractor is cut out of the system, the solvent is drained off, and the chips are usually subjected to the action of steam to removethe adhering solvent.

When all, or as much as is commercially feasible, of the desired solvent-soluble materials are with a load of fresh wood chips for subsequentextraction therefrom of rosin and the.li l; e. As e r u 'th e ree reetmentthe be o spent chips forms a relatively matted body which is difiicult to remove from the extractors. Removal is conventionally accomplished by opening the dooradjacent the bottom of the extractor and the usual top closure and hacking away at the residues by means of forks, picks, rods and the like in order to break up the matted-mass. In the usual case, this requires the services of two or more men andthe work is difiicult and mus be accompl s e er t yi g endit ne du to t e fee t et t e spen c s a e st h and steamin w e th t ct r is o e d f r di ha in th sp nt c p Nume ou at m t hav e m de i a f ort t facilitate the emo a of the s en chip hu f e ampl t u iliza on of a sc ew mecha sm o l ose and rem ve he p nt s ips ha e n su ges e E e t ve al o e n made he b ew o t e s en hins eit e hrou h th ten or botto thexexi ete bri ens of steam er a s un e eens e e e esitiv r su e- Non Q th epmee u es has; t m nowed p oren to bei ea ible; a dth u e ame u b r .s1iffieu and neeenemi al heu hi is, ha c nt ed the ain t e st t e t e pre t e i ommerc alep ret en n aee rdei e wi h my n entie t e rem a tram th ,ex raeter 2 the s en shin e residue,

resulting from the solvent extraction of rosin n w lik fie we h ps m bemate fa tate'd in a relatively simple "and eificacious manner; I have"'fouhd, in'geiieral, that 'if'the spent chips are subjectedto the action of'a hot, dilute acid solution;particularly at elevated temperaftures and pressures; the-'rnatted character of 'said's'pent'chips ismodified'sothat'w en the solution is removed, the solid residue myre sjny be rmoved'ithe'r by blowihg with'steam nder pressure or by any otherrneans. In'the preferred'rnanner of practicing my invention, the extractor containing the spent chips is closed and steam is admitted'thereinto until a pressure of everal atmospheres, for example, about 40 "to about pounds'p'er squareinch, is

, built up in the extractor? A dilute acid solution,

which is preferably one containing about fOl5 to 2.0% sulfuricacid, preferably at anelevat ed temperature, for exampl efatabout 15 0;190 degrees C., is admitted under pressure intoth -efxtractor at theto'pth'roughfa suitablejin'let' pipeat trolledrate and" allowed to' pass" throng chips; A suitable rate" of "introduction 'of the dilute acid' solution is about 11 600 800 poundsp'r minute when ,the' extractorgcontains "8tons of chips. ,When .the solution begins ito permeate the bed of chips and trickle from the bottom, a valve in the bottom of the extractor is opened and thereafter the solution is allowed to drain therefrom continuously until the process is completed. This usually requires from about one to several hours. As a result of such treatment, the matted character of the chips is modified so that, when the solution is drawn off, the solid residue may readily be removed from the extractor. This may be done with shovels or the like but is most conveniently accomplished by closing off the extractor, opening an auxiliary valve to a discharge pipe preferably located near the bottom of the extractor, and then admitting a gas, particularly steam, under positive pressure, into the extractor to blow out the residue. This operation takes only a very short time and is accomplished with a minimum of manual labor.

While I prefer to subject the spent chips to the initial action of steam before the introduction of the dilute acid solution, it is not necessary that this be done since, in the usual case, the spent chips will be at a somewhat elevated temperature as a result of the treatment thereof for extraction of the rosin, turpentine, pine oil, etc. therefrom.

While I find sulfuric acid to be most satisfactory because of its low cost and ready availability, I may use dilute solutions of other acids as, for example, hydrochloric acid, sulfurous acid, acetic acid, and the like acids of organic or inorganic character. In the case of sulfuric acid, a dilution of the order of 0.5% to about 2.0% is quite satisfactory although, of course, the degree of dilution may vary. In the case of other acids, the concentration thereof will vary depending upon the strength thereof but, in all cases, the solutions are dilute in character. The temperature of the acid solution is preferably elevated and it is particularly preferred that it be in excess of 100 degrees C., most desirably within the range of about 150 to 200 degrees C. It will, of course, be understood that the extractor and its associated parts should be made of or lined with material which will withstand the corrosive action of the acid solutions under the particular conditions under which they are employed. The acid solutions which are drained out of or otherwise removed from the extractors as a result of the treatment of the spent wood chips may, if desired, be treated to recover the valuables contained therein.

While I have described my invention in detail, no unnecessary limitations shall be read thereunto, the scope of said invention being set out in the claims.

What I claim as new and desire to protect by Letters Patent of the United States is:

l. The method of removing a matted bed of substantial thickness of spent wood chips from an extractor after the extraction of rosin from said chips by a solvent extraction procedure which comprises forcing a hot, dilute acid solution through said bed of spent wood chips until the matted character of said chips is modified, and, after drawing oil said solution, removing the solid residue from said extractor.

2. The method of removing a matted bed of substantial thickness of spent wood chips from an extractor after the extraction of rosin from said chips by a solvent extraction procedure which comprises forcing a hot, dilute sulfuric acid solution through said bed of spent wood chips until the matted character of said chips is modified, and, after drawing off said solution, blowing the solid residue from said extractor.

3. The method of removing a matted bed of substantial thickness of spent wood chips from an extractor after the extraction of rosin from said chips by a solvent extraction procedure which comprises forcing a hot, dilute acid solu- 7 tion, under a pressure in excess of atmospheric pressure, through said bed of spent wood chips Lmtil the matted character of said chips is modified, and, after drawing off said solution, subsequently removing the solid residue from said extractor.

4. The method of removing a matted bed of substantial thickness of spent wood chips from an extractor after the extraction of rosin from said chips by a solvent extraction procedure which comprises subjecting said spent chips to the action of steam, then forcing a dilute acid solution, under a pressure in excess of atmospheric pressure, through said bed of spent wood chips until the matted character of said chips is modified, and, after drawing off said solution, removing the solid residue from said extractor.

5. The method of removing a matted bed of substantial thickness of spent wood chips from an extractor after the extraction of rosin from said chips by means of a volatile petroleum hydrocarbon solvent which comprises subjecting said spent chips to the action of steam under pressure, forcing a dilute sulfuric acid solution, under a positive pressure, through said bed of spent wood chips until the matted character of said chips is modified, and, after drawing off said solution, subsequently removing the solid residue from said extractor.

6. In a method wherein a body of substantial depth of wood chips is placed in an extractor chamber having a height and a diameter of at least several feet and is treated with a solvent to remove rosin from said chips leaving a relatively matted residue of hot, spent chips in said extractor which is difficult to remove therefrom, the steps of removing said chips which comprise forcing a dilute acid solution, at elevated temperature and pressure, through said bed of chips until the matted character of said chip is modifled, and, after drawing off said solution, removing the solid residue from said extractor.

'7. In a method wherein a body of substantial depth of wood chips is placed in an extractor chamber having a height and a diameter of at least several feet and is treated with a volatile organic solvent to remove rosin from said chips leaving a relatively matted residue of hot, spent chips in said extractor which is difiicult to remove therefrom, the steps of removing said chips which comprise forcing a dilute sulfuric acid solution of about 0.5% to about 2.0% concentration, at a temperature exceeding degrees C. and under a pressure of several atmospheres, through said bed of chips until the matted character of said chips is modified, and then, after drawing off said solution, blowing the solid residue from said extractor.

8. In a method wherein a body of substantial depth of wood chips is placed in an extractor chamber having a height and a diameter of at least several feet and is treated with a volatile hydrocarbon solvent to remove rosin from said chips leaving a relatively matted residue of hot, spent chips in said extractor which is difficult to remove therefrom, the steps of removing said chips which comprise subjecting said spent chips to the action of steam under positive pressure,

forcing a dilute sulfuric acid solution of about 0.5% to about 2.0% concentration, at a temperature between about 150 and 200 degrees C. and under a pressure of several atmospheres,

through said bed of chips until the matted char- 5 acter of said chips is modified, and, after drawing off said solution, :blowing the solid residue from said extractor by means of steam under substantial positive pressure.

GERALD L. REASOR.

REFERENCES CITED The following references are of record in the file of this patent:

. 6 UNITED STATES PATENTS Number Name Date 1,678,089 Ullman July 24, 1928 1,845,487 Darling Feb. 16, 1932 2,110,546 Dreyfus Mar. 8, 1938 OTHER REFERENCES Manufacture of Pulp and Paper, 2nd edition, volume III, section 4, pages 74 and 75, McGraw- 10 Hill Book C0., 1927. 

